1. Field of the Invention
This invention relates to a pipe jacking apparatus, and more particularly to a pipe jacking apparatus adapted for being operated under remote control.
2. Description of the Prior Art
Generally, in laying a pipe, such as a sewer pipe, in the ground according to a pipe-jacking method, it has been customary that a shield type tunneling machine constituting a pipe jacking apparatus takes in charge of tunneling and withdrawal of muck; and a hydraulic thrust jack drives forward along a predetermined linear path a pipe, such as a reinforced concrete pipe, placed between the shield type tunneling machine and the thrust jack, in cooperation with the shield tunneling machine.
The shield type tunneling machine must be driven forward along a predetermined linear path by a thrust of the thrust jack. However, the shield type tunneling machines suffers from a variation in tunneling resistance due to a geological change, tending to divert from a predetermined linear path. A direction of moving shield type tunneling machine thus must be rectified. The tunneling machine in general is equipped with plural direction-adjusting jacks for rectifying a direction of moving shield type tunneling machine, and the outputs of respective direction-adjusting jacks are changed so as to rectify a direction of moving shield tunneling machine.
These direction-adjusting jacks, whether the shield type tunneling machine used is a pneumatic type or a sludge pressing type, is operated by an operator stationed at an atmospheric pressure zone at the rear of a partition wall in the shield tunneling machine. With a diametrically large shield tunneling machine for use in thrusting a pipe having a comparatively large inner diameter, for example, a pipe having a diameter of more than 900 mm, no problem arises in stationing at the shield tunneling machine an operator who operates the direction-adjusting jacks individually or collectively. On the other hand, a diametrically small shield tunneling machine for use in thrusting a pipe having a comparatively small diameter, for example, a sewer pipe having a diameter of 800 to 600 mm on the design, can not afford to station the operator thereat. Accordingly, even in the case where a diametrically small pipe is needed, a pipe having a diameter larger than required, for example, a pipe having a diameter of larger than 900 mm, and a shield type tunneling machine designed for thrusting such a diametrically large pipe must be employed, resulting in poor economy.
Furthermore, adjustment of a direction of moving shield type tunneling machine must be conducted by an operator according to instructions of a surveyor who makes a survey on a course of moving shield type tunneling machine by means of an optical unit, such as a transit, provided in a pit for thrusting the shield type tunneling machine into the ground. However, if a surveyor desires to know a degree of displacement of the shield tunneling machine from a predetermined course by means of light beams, such as laser beam, provided in the pit, the operator would intercept the optical path of the light beam to be irradiated to a target, namely, a center mark in the shield type tunneling machine, with the result that the light beam fails to reach the center mark.